Building upon results obtained during the first five years of the Program, the research activities conducted under this Project will be directed to identification and clinical application of scalp electrophysiological indices of human somatosensory cortical adaptation. In the first phase of the research, eight experimental studies will be conducted on a small sample of neurologically normal adults. Four experiments will be directed to vibrotactile adaptation, two to adaptation to surface-parallel brushing stimuli, and two to adaptation to electrical tooth-pulp stimuli. All categories of stimuli are being studied psychophysically by other Program investigators. In the case of the two cutaneous modalities the time-domain approach to measurement of evoked cortical activity will be supplemented using frequency-domain techniques that appear better matched to characteristics of the underlying neural response, and capable of providing functionally meaningful indices on a trial-by-trial basis. The primary goal of the eight proposed experiments is to identify stimulus protocols and response measurement techniques that can provide robust quantitative indices of CNS adaptation suitable for application in a clinical setting. The second phase of the research will utilize these indices for experimental study of hypothesized deficits in CNS adaptation in two orofacial sensory dysfunction groups (BSSO and TMD patients). The research is expected to lead to improved electrophysiological indices of both normal and disturbed cortical adaptive response. These neurophysiological measures will complement the psychophysical ones under development in the Program's other Projects, and thus provide additional means both for detecting and characterizing deficits resulting from orofacial trauma, and for monitoring the effects of treatment and the progress of recovery. In addition, they should help to establish a firm neuroscientific foundation for clinically useful psychophysical and behavioral measurements in humans, by providing interpretive bridges between these measurements and the more detailed observations available from prior neurophysiological studies of somatosensory cortical mechanisms in animal subjects.